1. Field of the Invention
The present patent application for industrial invention relates to a centrifugal separator with vertical axis of rotation or to a centrifuge with horizontal axis of rotation (decanter) provided with improved closing system.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.
FIG. 1 shows a centrifugal separator according to the prior art, generally indicated with reference number (100). The centrifugal separator (100) comprises a drum (1) mounted on a vertical rotary shaft (10).
A first axial conduit (11) is provided inside the drum (1), defining a distribution chamber. The first axial conduit (11) has a tapered lower end section (12) with downwardly increasing diameter. A second axial conduit (13) is disposed around the first axial conduit (11), being provided with a tapered lower end section (14) with downwardly increasing diameter.
Lamellar disks (15) are provided inside the drum (1), between the tapered sections (12, 14) of the two coaxial conduits, defining a separation area.
The centrifugal separator (100) provides for continuous separation of product (A) in two liquid phases (B, C) with different specific gravity; moreover, it provides for separation of an additional heavier phase (D) (solid sediments).
The product (A) is introduced by falling (or transferred with pump) in the rotary drum through a pipe (2); through the distribution chamber of the first conduit (11) the product reaches the bottom of the drum and is introduced in the separation area formed by the lamellar disks (15). The effect of the centrifugal force together with the presence of said disks (15) creates a separation between phases.
The liquid light phase (B) passes through the lamellar disks (15) and comes out of a first outlet (U1) of the drum, following the direction of arrows (B). The first outlet (U1) is disposed in the upper part of the drum, between the first axial conduit (11) and the second axial conduit (13).
The liquid heavy phase (C) comes out of a second outlet (U2) of the drum, following the direction of arrows (C). The second outlet (U2) is disposed between the second axial conduit (13) and the upper end of the drum (1) at a slightly lower level than the first outlet (U1).
The heavier solid sediments (D) are disposed in a peripheral area of the drum (1) and periodically ejected through a third outlet (U3) obtained in the peripheral part of the drum.
At the end of a work cycle, before the centrifugal separator is stopped, a large quantity of the light phase (B) (which is generally a valuable product, such as oil) remains inside the drum (1), being annularly stratified in the area proximal to the axis of rotation of the drum (1). Similarly, the heavy phase (C) forms the most peripheral layer. Consequently, a large quantity of water must be introduced into the drum (from the inlet of product (A)) in order to make the light phase (B) come out of the first outlet (U1) completely. In fact, water tends to come out with the heavy phase (C) through the second outlet (U2). If a large quantity of water is introduced, water is also able to “move” the light phase (B) towards the outlet (U1). Such a system involves a large waste of water and energy (energy absorbed by the water introduced in the rotary drum and coming out of it at high speed).
In order to solve such drawback caused by the large quantity of water needed, application of a closing device in the second outlet (U2), meaning the heavy phase outlet, is known. Such a closing device is normally open during the work cycle and is closed at the end of the cycle to recover the light phase trapped inside the drum.
Instead, in order to eject the heavier sediment (D), the drum (1) is provided with peripheral holes or slots that are intercepted by a sliding wall (61) (mobile bottom) that rotates together with the drum. In this way the third outlet is opened and closed (U3).
ES8600703, in the name of the same applicant, discloses a vertical centrifugal separator and a decanter, wherein a closing system of the heavy phase outlet is applied both to the vertical centrifugal separator and decanter and a closing system of the heavier sediment outlet is applied only to the vertical centrifugal separator.
The vertical centrifugal separator is provided with two liquid outlets (phases), of which at least one, i.e. the heavy liquid outlet (normally aqueous phase) is of free overflow type. The closing device closes the heavy phase outlet (by means of a “plug”) with the machine in operation and permits the complete emission of the valuable liquid (light phase) with the machine in operation, before the necessary intermittent discharge of sediments and the centrifugal feed phase with the recovery of the processing operations. The closing device simplifies the emptying of the light phase from the drum because it uses a very small flow and volume of heavy liquid (normally water) fed through the usual inlet of the process fluid. Otherwise, without closing device, the operation requires a large water flow and volume (with high consumption costs), also impairing the status of the liquid phases separated inside the drum, and consequently the status of the valuable light phase to be discharged, with evident negative consequences. The lack of the closing device also results in high energy consumption to accelerate the large water flow and volume used in the operation.
The horizontal centrifuge (traditional decanter) has liquid outlets, of free overflow type (straight overflow for the light phase and inverted or siphon overflow for the heavy phase). The closing device (“plug”) closes the heavy phase outlet to help emptying the light phase (valuable phase) from the drum, according to the same principle illustrated above for the Vertical Centrifuge (by introducing a limited flow and volume of heavy liquid or water). Also in this case, as for the Vertical Centrifuge, the drum can be emptied also without the closing device, but with a considerable amount of water, as already mentioned for the Vertical Centrifuge, with the same negative effects. The closing device is provided with a “normally open” plug that is closed when the device is actuated.
ES2338964 discloses an improved decanter compared to ES8600703, wherein the light phase outlet is obtained in the end flange of the drum and the heavy phase outlet is obtained by means of a radial pipe in association with an obturating disk inside the drum. The disk is situated between the outlets of the two phases in the proximity of said radial pipe. The heavy phase outlet is of inverted overflow type.
Said decanter is provided with a service opening situated in the end flange of the drum in peripheral position with respect to the light phase outlet. A closing device is used to open and close said service opening.
The closing device is normally closed and is opened at the end of the work cycle to discharge and recover the light phase completely through said service opening. Obviously, in such a case, unlike traditional decanters, it is not necessary to introduce a flow and volume of heavy service liquid (normally water) through the service opening, it being simply necessary to open the plug.
EP 1 712 289 discloses a closing device applied to a vertical centrifugal separator that is substantially similar and applicable in the same way as the closing device of ES8600703, but with a different purpose: to wash the interior of the drum for its entire volume, after emptying the valuable light phase from the drum and discharging the sediments. The closing device of the heavy phase is the means that allows for accurate cleaning, feeding the drum with water (or solvent) or fluid for cleaning and rinsing, instead of separation liquid. When the plug is open, the internal parts of the outlet branch of the heavy phase are washed. When the plug is closed, the outlet areas of the light phase, which are difficult to reach without the closing device, are washed. In fact, without the closing device, the consumption of detergent, water and energy would be very high.
The closing systems of the prior art are of hydraulic type (using water as work liquid). The centrifugal pressure of the water is self-generated by the rotation of the drum (by centrifugal force). These hydraulic systems operate when both the inlet product feed flow and the outlet separate products flow are interrupted.
Said hydraulically-controlled closing devices are impaired by several drawbacks. In fact, the closing devices get dirty during the work cycle, not only during activation, but also during the entire separation phase carried out by the centrifugal machine, regardless of being a vertical or horizontal machine.
The service liquid used in the hydraulically-controlled closing device is water. Coupling between fixed and mobile parts of the device is a precision, sliding, watertight coupling. Because of the service water subject to centrifugal force, pressure in the coupling areas is very high and sliding must be guaranteed.
The already separated or centrifuged liquid contains solid sediments, especially in the case of the decanter, which is a rough-processing centrifuge compared to the Centrifugal Separator, but also in the case of a Centrifugal Separator. The service liquid is easily contaminated with the process liquid because they are adjacent. Therefore, solid sediments are rapidly deposited in the sliding areas of the closing device, thus impairing its operation. Frequent cleaning is necessary, although difficult and time consuming, since it requires disassembly the affected parts.
U.S. Pat. No. 2,218,532 discloses a centrifugal separator comprising an electromagnet connected to a valve to open/close an opening disposed in the lower part of the drum to discharge solid sediments.
The purpose of the present invention is to eliminate the drawbacks of the prior art, disclosing a centrifugal separator or decanter provided with a closing system to close/open the liquid heavy phase outlet that is efficient, effective and reliable.
Another purpose is to disclose a centrifugal separator provided with a closing system to open/close the solid sediments outlet that is efficient, effective and reliable.
Another purpose of the present invention is to provide such a closing device that is simple to make and install and capable of minimizing maintenance operations.